The invention relates to a method for controlling an air conditioning system in a vehicle to reduce the humidity entering into the interior of the vehicle.
In most motor vehicles the fresh air intake of the heating and air conditioning system occurs almost exclusively through a gap that is produced between the engine hood and the windshield. In the event of heavy rain or driving through a carwash, considerable amounts of water may penetrate into the areas that house the equipment units that are located below the engine hood. In order to enable relatively dry fresh air to flow through the fresh air intake port into the interior of the vehicle, or rather into the heating and air conditioning system, the equipment area exhibits design features for separating air and water, that is, for the removal of water.
The configuration of such design features is typically based on the maximum amount of water that can be expected to occur, as for example in the case of tropical rain downpours or even in the case of U.S. carwashes that clean the vehicles with an enormous amount of water. In such cases, it has to be guaranteed that even under these extreme conditions there will be no intake of water, even when the air conditioning system is running at a high air flow rate. The result of these design features is often that the fresh air intake exhibits a higher flow resistance, a state that is disadvantageous to the targeted air volume and the acoustic properties of the blower.
In order to draw in as much dry air as possible, DE 10 2004 055 259 B3 discloses an air supply device that is intended for the passenger compartment of a vehicle and that has a rotating element that is connected upstream of an air conditioner blower and is located in the axial intake region of the air conditioner blower. The rotating element covers the air entry region in such a manner that all of the droplets that are drawn in impinge on this element. The rotational motion of the element causes the intake droplets to be thrown outwards, where they are caught by droplet catching elements and then conveyed away. Such an air supply device is extremely expensive and has a high space requirement.
As an alternative, DE 10 2006 018 905 A1 discloses an air duct system for conveying the intake air in a vehicle. In this case the air duct system is provided with water removing means for separating the water from the intake air. The drawback with this system is that the water removing means has just a limited holding capacity and is thus inadequate for use with extremely large quantities amounts of water. All of the design features have in common that they incur additional costs.
The object of the invention is to provide a method that makes it possible to reduce the humidity entering into the passenger compartment in a simple and cost effective way. The invention achieves this object with the subject matter of the independent patent claim. Advantageous further developments are the subject matter of the dependent patent claims.
The invention is based on the recognition that it is possible to reduce the entry of humidity by suitably controlling the air conditioning system. The inventive method for controlling the air conditioning system is characterized in that a measure for the amount of water collected at the fresh air intake port is determined as a function of a sensor signal, and that as a function of the determined measure for the amount of water collected at the fresh air intake port, the air conditioning system is controlled in such a manner that the amount of air that is drawn in through the fresh air intake port is reduced. Therefore, the fundamental idea is that a sensor signal is evaluated in a first step and that this sensor signal allows conclusions to be drawn about the amount of water that has collected in the hood gap. If a corresponding amount of water is detected, then in the next step the system can respond to the risk of drawing in water with suitable measures that reduce the amount of fresh intake air.
It is advantageous to reduce the amount of air drawn in through the fresh air intake port at the point when the determined measure for the amount of water that has collected at the fresh air intake port exceeds a pre-set limit value. In this way the control of the air conditioning system is changed only when extremely large masses of water are on hand. A negative impact on the vehicle passengers is suppressed because the change in the control of the air conditioning system is generally implemented for only a short period of time (during a sudden downpour or while driving through a carwash).
In certain embodiments, the aforementioned method of reducing the amount of air drawn in through the fresh air intake port may be applied when the vehicle is driven through a carwash where a high quantity of water can be expected. The drive-through of a carwash can be detected by the evaluation of additional signals. Hence, in one advantageous embodiment of the invention the amount of air that is drawn in through the fresh air intake port can be reduced when, for example, the speed of the vehicle is also less than a pre-set speed limit value.
Another aspect of the invention is to reduce the amount of air drawn in through the fresh air intake port only when one or more additional criteria are met, such as when the blower output of the air conditioning system is greater than a pre-set blower limit value and/or if additionally the outside temperature is higher than a pre-set outside temperature limit value (e.g., higher than the freezing point). An evaluation of the outside temperature is practical, especially if there is the risk that the detecting sensor will ice up and thus would deliver, despite the dryness, a signal that would indicate a very high quantity of water in front of the fresh air intake port.
In order to reduce the amount of air that is drawn in through the fresh air intake port, various measures for controlling the air conditioning system can be implemented in an advantageous way. For example, the amount of air that is drawn in through the fresh air intake port can be reduced by enlarging the opening angle of the air recirculation flap and/or by reducing the blower voltage. In extreme cases, it is possible to even throttle or totally close the fresh air flap so that no water can be entrained in the intake air.
In principle the amount of air that is drawn in through the fresh air intake port is reduced only until at least one of the conditions for initiating the reduction of the amount of intake air is no longer fulfilled. If additional signals, such as speed and outside temperature are evaluated, then the change in the control of the air conditioning system may be cancelled even if a higher speed is determined or the outside temperature falls below the freezing point.
In order to ensure that the vehicle passengers will not be negatively affected by the change in the control of the air conditioning system, one aspect of the invention is to ensure that the aforementioned modified air intake control is not implemented too long. Ideally the amount of air that is drawn in through the fresh air intake port can be reduced only until a targeted time interval has expired. In order to prevent fogging of the windows, the humidity in the interior or rather a signal that correlates with the humidity in the interior of the vehicle and/or the signal of a fogging sensor can be evaluated. If the interior humidity exceeds a pre-set limit value, then the air conditioning system can be operated again in the original control mode or switched into a de-humidifying mode.
In order to determine the amount of water that has collected at the fresh air intake port or rather a variable that correlates with the same, a variety of sensors can be used. It can be a sensor that has been installed exclusively for this purpose or an expanded sensor. It is advantageous if the measure for the amount of water that has collected at the fresh air intake port can be determined in the equipment area as a function of the signal of a fluid level indicating sensor that indicates the current accumulation level at a specific spot. Alternatively, or in addition, the amount of water that has collected at the fresh air intake port can be determined as a function of the signal of an optical sensor unit for determining the droplet flight in front of the fresh air intake port.
As an alternative or in addition, any existing sensor can also be used if capable of delivering information about the amount of water that has accumulated in the equipment area (e.g., at the fresh air intake port). Especially appropriate for this purpose is a rain sensor that is typically installed in the base of the internal mirror in vehicles with automatic wipers.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of one or more preferred embodiments when considered in conjunction with the accompanying drawings.